JPH0656566B2 - Vibration suppression control system for article transfer device - Google Patents

Description

The present invention relates to an article transfer device that moves an article gripper to transfer an article, and suppresses vibration of a drive mechanism section to position the article gripper with high accuracy. The present invention relates to a vibration suppression control system of an article transfer device for improving the accuracy of the.

(Prior Art) In the positioning control of this kind of article transfer device, a negative feedback control method of comparing an output signal (position signal) of a position sensor with a target position signal and driving a drive mechanism by the difference (positional error) Is used. In this negative feedback control, when a position error occurs due to a disturbance or the like, a position signal having a negative polarity is fed back, so that a correction force that reduces the position error acts on the drive mechanism, and the position error can be corrected. However, when the drive mechanism has mechanical resonance and its frequency is close to the desired control band, the phase delay between the correction force and the movement of the drive mechanism is close to the mechanical resonance frequency as shown in FIG. In 1
The angle becomes 80 degrees, and the feedback position signal, which has a negative polarity, reverses to a positive polarity.

In FIG. 2, 21 is an amplitude characteristic curve of the article transfer mechanism,
22 is a phase characteristic curve of the article transfer mechanism.

At this reverse rotation frequency, the negative feedback position signal with respect to the position error reverses to the positive polarity, so that it acts on the drive mechanism to increase the position error, and the positioning control system becomes unstable. Therefore, the following two methods have been well known as damping methods for stably controlling a drive mechanism having mechanical resonance.

In order to make the mechanical resonance frequency above the desired control band,
A method for increasing the rigidity of the mechanical system (first method).

A method (second method) of controlling the mechanical resonance frequency component from the position signal by an electric circuit such as a low-pass filter or a band reject filter.

(Problems to be Solved by the Invention) The first method described above is an effective method as a vibration damping method because the position signal does not include a mechanical resonance component, but is not effective for increasing the rigidity of the mechanical system. Since a mechanical material having a low density and a high rigidity is required, there is a certain limit to the high rigidity unless a breakthrough in material technology is made.

The second method is a method that does not involve mechanical changes because it electrically suppresses mechanical resonance components, but the phase delay in an electric circuit is lower than the mechanical resonance frequency by inserting a filter or the like. There is a drawback that the tracking error [(target value-actual position) / target value] generated from the frequency region increases due to this phase delay.

(Object of the Invention) It is an object of the present invention to provide a vibration suppression control system for an article transfer device which does not involve a mechanical change and can minimize an increase in tracking error due to a phase delay.

(Means for Solving the Problems) In order to achieve the above object, a first invention is an article gripping section for gripping an article, and a drive mechanism including a motor for moving the article gripping section vertically or horizontally. A position sensor that detects the position of the article gripping portion, and a control portion that performs sampling control of the drive mechanism according to the output of the position sensor, the output of the control portion via a zero-order hold circuit and a power amplifier. In the article transfer device adapted to apply the voltage to the motor, the sampling frequency of the control unit is made to match the mechanical resonance frequency of the drive mechanism. A second aspect of the present invention is an article gripping section for gripping an article, a drive mechanism including a motor for moving the article gripping section up and down or left and right, a position sensor for detecting the position of the article gripping section, A controller for controlling sampling of the drive mechanism according to an output of a position sensor, wherein the output of the controller is applied to the motor through a zero-order hold circuit and a power amplifier. The mechanical resonance frequency of the drive mechanism is measured from the output of the position sensor, and the sampling frequency of the control unit is corrected and controlled so that the sampling frequency coincides with the measured frequency.

(Operation) The present invention is based on the transmissibility of the zero-order hold circuit in sampling control (ratio of output signal amplitude to input signal amplitude).
Can be made zero at the sampling frequency, so that the mechanical resonance frequency component is selectively suppressed from the position signal.

(Embodiment) FIG. 1 is a diagram for explaining a first embodiment of the present invention,
1 is an article gripper, 2 is a wire rope, 3 is a motor, 4 is a drive pulley, 5 is a position sensor, 6 is a position signal line, and 7 is a position signal line.
Is a drive current calculator, 8 is a target value input line, 9 is a difference signal line,
Reference numeral 10 is a zero-order hold circuit, 11 is a power amplifier, 12 is an idler pulley, 13 is a frequency adjustable sampling signal generator, and the drive current calculation unit 7 and the sampling signal generator 13 constitute a control unit.

The article gripper 1 directly connected to the wire rope 2 has a motor 3
It is frictionally driven by a drive pulley 4 directly connected to.
The position signal is detected by the position sensor 5 directly connected to the drive pulley 4, and is input to the drive current calculator 7 via the position signal line 6. This position signal is subtracted by the drive current calculator 7 from the target value transmitted from the host device via the target value input line 8. This difference signal is output to the zero-order hold circuit 10 via the difference signal 9. The difference signal held by the zero-order hold circuit 10 for the sampling period is amplified by the power amplifier 11 to drive the motor 3. In the positioning control in which the target value is set to zero, the polarity of the position signal is reversed by the drive current calculation unit 7, so that the article gripping unit 1 is subject to disturbance or the like.
When a position error such as a deviation from the target position in the positive direction occurs, a negative position signal is given to the motor 3 via the power amplifier 11, and the motor 3 rotates in the negative direction to correct the position error. It

However, when the drive mechanism constitutes a mechanical resonance system,
As described above, from the drive input of the motor 3 to the article gripper 1
It can be seen from the characteristic curves 21 and 22 in FIG. 2 that the phase delay rapidly increases due to mechanical resonance and the amplitude of the position signal increases near the mechanical resonance frequency. Therefore, when a positioning control system is configured by using a drive mechanism having such a mechanical resonance characteristic, the transfer delay due to the mechanical resonance is added to the phase delay of the drive current calculation unit 7 and the electric power amplifier 11 in the electric circuit. Then, when the magnitude reaches 180 degrees, the position signal phase for the motor 3 is reversed from the negative polarity to the positive polarity. When a slight disturbance acts on such a mechanical resonance system and a position error occurs in the article gripper 1, a positive mechanical resonance position signal component is fed back to the motor 3,
Since the position error signal is amplified and returned to the motor 3 again, the position error of the article gripper 1 increases geometrically,
Finally, the positioning control system oscillates.

However, as shown in FIG. 3, since the transmissibility 31 at the sampling frequency of the zero-order hold circuit 10 is zero, if the sampling frequency is matched with the mechanical resonance frequency,
The mechanical resonance frequency component can be selectively attenuated, and the positioning control system can be stabilized. In this embodiment, the mechanical resonance frequency of the drive mechanism is measured by a method well known to those skilled in the art, for example, a modal analysis device, and the generation frequency of the frequency adjustable sampling signal generator 13 is set to the mechanical resonance. Adjust to match the frequency.

If the vibration damping control method is applied to a system in which the weight of the article gripping portion 1 changes with the gripping operation and the mechanical resonance frequency fluctuates, the resonance component suppressing effect may be diminished. However, according to the experiment, the suppression effect of the zero-order hold circuit 10 is −60d in the range of ± 10% around the sampling frequency.
Since it was found that the value was B or less, the present vibration suppression control method is effective for a system in which the weight fluctuation is relatively small.

FIG. 4 is a diagram for explaining a second embodiment for a system in which the weight change of the article gripping portion 1 accompanying the gripping operation is large and the resonance component suppressing effect is small in the first embodiment, and 41 is a Fourier series operation. 42, a sampling signal oscillator controller, 4
Reference numeral 3 denotes a sampling signal oscillator, which constitutes a control unit together with the drive current calculation unit 7.

In this embodiment, since the mechanical resonance frequency of the drive mechanism is automatically detected, the sampling signal oscillator control unit 42
Instructs the drive current calculator 7 to generate an impulse signal via the drive command line 15. The impulse signal generated by the drive current calculator 7 is amplified by the power amplifier 11 via the zero-order hold circuit 10 to drive the motor 3. Motor 3
The impulse response of the article gripper 1 driven by is input to the Fourier series calculation unit 41 via the position signal line 6, and the Fourier series is calculated there. The sampling signal oscillator controller 42 detects the mechanical resonance frequency from the Fourier series by a method known to those skilled in the art. Next,
The sampling signal oscillator control unit 42 reads the mechanical resonance frequency from the Fourier series operation unit 41, and adjusts the sampling signal oscillator 43 so as to match the reading frequency. Specifically, this sampling signal oscillator 4
If 3 is constructed using an integrated circuit generally sold as a voltage controlled oscillator (VCO), the oscillation frequency can be adjusted by the control voltage of the VCO. Therefore, in order to obtain the desired frequency, the sampling signal oscillator control unit 42 may calculate the control voltage from the specification value of the read mechanical resonance frequency and give it to the sampling signal oscillator 43.

As described above, in the present invention, the mechanical resonance frequency of the drive mechanism is detected from the position signal, and the oscillation frequency of the sampling signal oscillator is adjusted so that the sampling frequency matches this frequency. By utilizing the characteristic that the transmissibility at the sampling frequency can be made zero, the mechanical resonance frequency component can be selectively attenuated to stabilize the positioning control system, and the tracking error with respect to the suppression method by the conventional filter etc. Can be made smaller.

The functions of the drive current calculator 7 and the sampling signal generators 13 and 43, the Fourier series calculator 41, and the sampling signal oscillator controller 42, which are surrounded by the dotted lines in FIGS. Since it can be realized by one processor, it is possible to make the drive control circuit compact and economical.

(Effects of the Invention) As described above, according to the present invention, the mechanical resonance frequency of the drive mechanism is detected from the position signal, and the sampling frequency of the control unit is adjusted so that the sampling frequency matches this frequency. , The characteristic of the zero-order hold circuit that can set the transmissibility at the sampling frequency to zero can be used to selectively attenuate the mechanical resonance frequency component to stabilize the positioning control system and suppress it with conventional filters. There is an advantage that the tracking error can be made smaller than the method.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a first embodiment of the present invention,
2 is a diagram showing the transfer characteristic of the article transfer mechanism from the drive input of the motor to the article gripping part, FIG. 3 is a diagram showing the transfer characteristic of the zero-order hold circuit, and FIG. 4 is the embodiment of FIG. It is a block diagram shown. DESCRIPTION OF SYMBOLS 1 ... Article holding part, 2 ... Wire rope, 3 ... Motor, 4 ...
Drive pulley, 5 ... Position sensor, 6 ... Position signal line, 7
... drive current calculator, 8 ... target value input line, 9 ... difference signal line,
10 ... Zero-order hold circuit, 11 ... Power amplifier, 12 ... Idler pulley, 13 ... Frequency adjustable sampling signal generator, 14 ... Sampling signal line, 15 ... Driving command line,
21 ... Amplitude characteristics of article transfer mechanism, 22 ... Phase characteristics of article transfer mechanism, 31 ... Zero-order hold circuit transmissibility, 32 ... Transmissivity from zero-order hold circuit to position signal, 41 ... Fourier series operation unit, 42 ... Sampling signal oscillator controller.

Claims (2)

[Claims] 1. An article gripping section for gripping an article, a drive mechanism including a motor for moving the article gripping section vertically or horizontally, and a position sensor for detecting the position of the article gripping section.
In an article transfer device, comprising: a control unit that controls sampling of the drive mechanism according to the output of the position sensor, and applies the output of the control unit to the motor through a zero-order hold circuit and a power amplifier. A vibration damping control system for an article transfer device, wherein a sampling frequency of the control unit is matched with a mechanical resonance frequency of the drive mechanism. 2. An article gripper for gripping an article, a drive mechanism including a motor for moving the article gripper vertically or horizontally, and a position sensor for detecting the position of the article gripper.
In an article transfer device, comprising: a control unit that controls sampling of the drive mechanism according to the output of the position sensor, and applies the output of the control unit to the motor through a zero-order hold circuit and a power amplifier. The mechanical resonance frequency of the drive mechanism is measured from the output of the position sensor, and the sampling frequency of the control unit is corrected and controlled to match the sampling frequency with the measurement frequency. Vibration control method.